Herein are described intermediate transfer members, and more specifically, intermediate transfer members useful in transferring a developed image in an electrostatographic, for example xerographic, including digital, image on image, and the like, machines or apparatuses. In embodiments, there are selected intermediate transfer members comprising a layer or substrate comprising a filled polymer, such as a filled polyimide, and for example, a polyaniline filled polyimide. In embodiments, the resistivity of the polyaniline filled polyimide is relatively high. In embodiments, the polyaniline has a relatively small particle size. In embodiments, a combination of polyaniline and polyimide allows for a weldable intermediate transfer member to be prepared. In embodiments, the weldable intermediate transfer member dispenses with the need for puzzle cut seams, which are highly labor intensive. The net manufacturing cost to produce the weldable intermediate transfer members, in embodiments, is lowered. In embodiments, the weldable intermediate transfer members are imageable.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles, which are commonly referred to as toner. Generally, the electrostatic latent image is developed by bringing a developer mixture into contact therewith. The developer mixture can comprise a dry developer mixture, which usually comprises carrier granules having toner particles adhering triboelectrically thereto, or a liquid developer material, which may include a liquid carrier having toner particles, dispersed therein. The developer material is advanced into contact with the electrostatic latent image and the toner particles are deposited thereon in image configuration. Subsequently, the developed image is transferred to a copy sheet. It is advantageous to transfer the developed image to a coated intermediate transfer web, belt or component, and subsequently transfer with very high transfer efficiency the developed image from the intermediate transfer member to a permanent substrate. The toner image is subsequently usually fixed or fused upon a support, which may be the photosensitive member itself, or other support sheet such as plain paper.
In electrostatographic printing machines wherein the toner image is electrostatically transferred by a potential between the imaging member and the intermediate transfer member, the transfer of the toner particles to the intermediate transfer member and the retention thereof should be as complete as possible so that the image ultimately transferred to the image receiving substrate will have a high resolution. Substantially 100% toner transfer occurs when most or all of the toner particles comprising the image are transferred and little residual toner remains on the surface from which the image was transferred.
Intermediate transfer members allow for positive attributes such as enabling high throughput at modest process speeds, improving registration of the final color toner image in color systems using synchronous development of one or more component colors using one or more transfer stations, and increasing the range of final substrates that can be used. However, a disadvantage of using an intermediate transfer member is that a plurality of transfer steps is required allowing for the possibility of charge exchange occurring between toner particles and the transfer member which ultimately can lead to less than complete toner transfer. The result is low-resolution images on the image receiving substrate and image deterioration. When the image is in color, the image can additionally suffer from color shifting and color deterioration. In addition, the incorporation of charging agents in liquid developers, although providing acceptable quality images and acceptable resolution due to improved charging of the toner, can exacerbate the problem of charge exchange between the toner and the intermediate transfer member.
In embodiments, the resistivity of the intermediate transfer member is within a range to allow for sufficient transfer. It is also desired that the intermediate transfer member have a controlled resistivity, wherein the resistivity is virtually unaffected by changes in humidity, temperature, bias field, and operating time. In addition, a controlled resistivity is important so that a bias field can be established for electrostatic transfer. It is desired that the intermediate transfer member not be too conductive as air breakdown can possibly occur.
Attempts at controlling the resistivity of intermediate transfer members have been accomplished by, for example, adding conductive fillers such as ionic additives and/or carbon black to the outer layer. For example, U.S. Pat. No. 6,397,034 discloses use of fluorinate carbon filler in a polyimide intermediate transfer member layer. However, there are problems associated with the use of such additives. In particular, undissolved particles frequently bloom or migrate to the surface of the polymer and cause an imperfection in the polymer. This leads to nonuniform resistivity, which in turn, causes poor antistatic properties and poor mechanical strength. The ionic additives on the surface may interfere with toner release. Furthermore, bubbles may appear in the conductive polymer, some of which can only be seen with the aid of a microscope, others of which are large enough to be observed with the naked eye. These bubbles provide the same kind of difficulty as the undissolved particles in the polymer, namely poor or nonuniform electrical properties and poor mechanical properties.
In addition, the ionic additives themselves are sensitive to changes in temperature, humidity, and operating time. These sensitivities often limit the resistivity range. For example, the resistivity usually decreases by up to two orders of magnitude or more as the humidity increases from 20% to 80% relative humidity. This effect limits the operational or process latitude.
Moreover, ion transfer can also occur in these systems. The transfer of ions leads to charge exchanges and insufficient transfers, which in turn causes low image resolution and image deterioration, thereby adversely affecting the copy quality. In color systems, additional adverse results include color shifting and color deterioration. Ion transfer also increases the resistivity of the polymer member after repetitive use. This can limit the process and operational latitude and eventually the ion-filled polymer member will be unusable.
Use of polyaniline filler in a polyimide has been disclosed in U.S. Pat. No. 6,602,156. However, the patent discloses a polyaniline filled polyimide puzzle cut seamed belt. The use of the polyaniline filled polyimide puzzle cut seamed belt provides a belt, which has improved mechanical and electrical properties over other filled belts. However, manufacture of the puzzle cut seamed belt is labor intensive and very costly, and the puzzle cut seam, in embodiments, is sometimes weak. The manufacturing process for a puzzle cut seamed belt requires a lengthy high temperature and high humidity-conditioning step. For the conditioning step, each individual belt is rough cut, rolled up, and placed in a conditioning chamber that is environmentally controlled at 45° C. and 85 percent relative humidity, for approximately 20 hours. Another 3 hours is required to bring the belt back down to ambient conditioning to prevent condensation and watermarks before it can be removed from the conditioning chamber. This conditioning operation is required to bring the belt into the proper resistivity range for use in a color printer. The conditioning step necessitates that sheets of the belt material be cut roughly to size prior to conditioning. This makes it virtually impossible to automate the manufacturing process for puzzle cut seamed belts. Without the 24-hour high temperature and high humidity conditioning step, the belt's electrical properties and hence image quality, will not be stable for several months.
Also, after the 1-day high temperature and high humidity-conditioning step, puzzle cut seamed belts are then additionally prepared by using tape or glue at the seam. This step is followed by the highly labor intensive step of having an operator manually zip the puzzle cut pieces together with their fingers. Once seamed, the strength of the puzzle cut seam is limited by the strength of the puzzle cut piece necks. Most belt break failures occur when the puzzle necks break.
Smaller circumference intermediate transfer belts are made by extrusion or spin casting. However, extrusion and spin casting are not cost effective for belts requiring larger circumferences. Larger circumference belts are necessary in color tandem engine architecture machines.
Therefore, it is desired to provide a weldable intermediate transfer belt, which has improved transfer ability and improved copy quality. It is also desired to provide a weldable intermediate transfer belt that does not have puzzle cut seams, but instead, has a weldable seam, thereby providing a belt that can be manufactured without such labor intensive steps as manually piecing together the puzzle cut seam with fingers, and without the lengthy high temperature and high humidity conditioning steps. Further, it is desired to provide a belt that has a stronger seam than current puzzle cut seams. It is also desired to provide a higher circumference weldable belt for color machines.